The objective of this proposal is to characterize the roles of nitric oxide (NO)/cGMP signal transduction in the neointimal response to vascular injury. Vascular injury induces smooth muscle cells in the media to migrate into the intima, where they proliferate and synthesize extracellular matrix, ultimately compromising the lumen. Recent studies in animal models and in patients with coronary artery disease have suggested that increasing NO levels at the site of vascular injury inhibits neointima formation. NO acts, in part, by stimulating soluble guanylate cyclase (sGC), a heterodimer composed of alpha and beta subunits, to produce cGMP leading to activation of cGMP-dependent protein kinase Z(cGDPK). In vitro, NO appears to modulate many vascular cell functions, inhibiting smooth muscle cell proliferation, migration, and extracellular matrix synthesis and stimulating endothelial cell proliferation and smooth muscle cell apoptosis. Preliminary evidence suggests that sGC and cGDPK are decreased in neointimal smooth muscle cells of injured blood vessels. We hypothesize that vascular cell NO/cGMP signal transduction has an important role in attenuating neointima formation and that decreased sGC and cGDPK limit the ability of NO to inhibit neointima formation. To test these hypothesis, adenovirus-mediated gene transfer will be used to determine the effect of altering NO/cGMP signal transduction on the neointimal response to vascular injury. In Specific Aim 1, vascular cells in culture will be infected with adenoviral vectors specifying a mutant dominant-negative sGC alpha1 subunit, wild-type cGDPK, and a mutant constitutively-active cGDPK. The effects of altering NO/cGMP signal transduction on vascular cell functions which contribute to neointima formation will be identified. In Specific Aim 2, sGC and cGDPK expression will be correlated with the changes in vascular cell functions associated with balloon-induced vascular injury in a rat carotid artery model. In Specific Aim 3, adenovirus-mediated gene transfer will be used to investigate the effect of modulating NO/cGMP signal transduction on vascular injury-induced neointima formation, as well as re- endothelialization, and smooth muscle cell proliferation, apoptosis and extracellular matrix synthesis. Neointima formation contributes to the restonosis process which frequently follows percutaneous angioplasty. Understanding the roles of the NO/cGMP signal transduction system in modulating the response to vascular injury may provide novel therapeutic approaches for the treatment of restonosis that percutaneous angioplasty.